The present invention relates to a defect-inspecting apparatus and a defect-inspecting method, which are used for inspecting defects such as a scratch or a particulate foreign material by discrimination; the defects occur in a planarization fabrication process based on polishing or grinding fabrication technique, which is used in semiconductor production and in magnetic head production.
As a prior art that inspects a foreign material, which adheres to a semiconductor wafer where a circuit pattern is formed, by discriminating the foreign material from a circuit pattern, Japanese Patent Application Laid-Open No. Hei 3-102248 (prior art 1) and Japanese Patent Application Laid-Open No. Hei 3-102249 (prior art 2) are known. To be more specific, in the prior arts 1 and 2, the following are described: a first photoelectric conversion element detects a foreign material on a semiconductor substrate by emphasizing the foreign material using oblique illumination; in addition to it, a second photoelectric conversion element detects the foreign material by emphasizing an edge of a circuit pattern, which is a background on the semiconductor substrate, using incident (vertical) illumination; after that, a foreign material detection signal obtained from the first photoelectric conversion element is divided (or is processed by other operation) by a detection signal obtained from the second photoelectric conversion element; and then, the foreign material is detected by emphasizing the foreign material detection signal.
In addition, as a prior art that separates a foreign material adhering to a surface of a silicon wafer from a crystal defect existing on the surface in order to inspect them, Japanese Patent Application Laid-Open No. Hei 9-304289 (prior art 3) is known. To be more specific, in the prior art 3, the following are described: a low-angle light receiving system, of which an elevation angle with reference to a surface of a silicon wafer is 30° or less, and a high-angle light receiving system having an elevation angle higher than this are provided; the low-angle light receiving system and the high-angle light receiving system receive scattered light, which is obtained by irradiating with a laser beam the surface of the silicon wafer substantially perpendicularly; and a foreign material and a crystal defect are inspected by discriminating the scattered received only by the high-angle light receiving system, which is treated as a crystal defect, from the scattered received by both the low-angle light receiving system and the high-angle light receiving system, which is treated as an adhered foreign material.
Moreover, as a prior art that discriminates a foreign material and a flaw existing on a surface of a semiconductor wafer from a minute dotty concave portion, which will not cause a failure when producing a circuit pattern, without misidentification in order to inspect them, Japanese Patent Application Laid-Open No. Hei 11-142127 (prior art 4) is known. To be more specific, in the prior art 4, the following are described: each of two pieces of illumination light having a wavelength different from each other is condensed and irradiated at the same point on a surface of a semiconductor wafer using a low incident angle and a high incident angle (each of the angles is different from each other); each scattered light from the condense point is received and photoelectric-converted separately according to each of the two wavelengths; and utilizing intensity difference between signals (that is to say, utilizing the fact that from a dotty concave portion, scattered light intensity of illumination light having a low incident angle is weakened), a foreign material and a flaw existing on the surface of the semiconductor wafer are inspected by discriminating the foreign material and the flaw from the dotty concave portion.
By the way, as typical planarization fabrication technique that is used for an object to be fabricated (for example, an insulating layer) at the time of semiconductor production and magnetic head production, there is CMP (Chemical Mechanical Polishing). The CMP is a planarization technology that scatters free abrasive such as silica on a polishing pad, and that polishes a surface of the object to be fabricated. Moreover, as the planarization fabrication technique, grinding fabrication technique may also be used. The grinding fabrication technique buries a fixed abrasive such as a diamond in a polishing pad to perform grinding fabrication in a similar manner. In the polishing or the grinding fabrication technique, on the surface of the object to be fabricated (for example, insulating layer on the semiconductor substrate (wafer)) after polishing or grinding, a scratch showing shape variations, which is a polishing or a grinding flaw, may be produced. In this manner, if a scratch showing shape variations is produced on the surface of the object to be fabricated in the semiconductor production and the magnetic head production, etching will become insufficient in wiring formed on the scratch, which causes a failure such as short circuit. For this reason, it is necessary to observe a wafer polished surface or a ground surface after polishing or grinding and to monitor a state in which a scratch showing shape variations has been produced. If many scratches have been produced, polishing or grinding conditions should be reviewed so that the conditions correspond to the shapes of the scratches. In addition to it, at the same time, if a foreign material adheres, a failure such as an insulation failure or a short circuit of wiring formed on it is caused. If many foreign materials adhere, measures such as equipment scrubbing, which are different from those against a scratch, become necessary. More specifically, in a polishing process or a grinding process for the object to be fabricated (for example, the insulating layer on the semiconductor substrate), a foreign material and a scratch showing shape variations are separately monitored, and appropriate measures are required to be taken against each.
However, all of the prior arts from 1 to 4 did not take the following point into consideration: when the polishing process or the grinding process is performed for the object to be fabricated (for example, the insulating layer on the semiconductor substrate), a scratch showing shape variations, which is produced on the surface, and an adhered particulate foreign material, are inspected while discriminating between them.
Moreover, as regards a size of the scratch showing shape variations, a width W ranges from 0.2 to 0.4 μm approximately, and a depth D ranges from about several nm to about 100 nm (even a very deep scratch), which is very minute. Therefore, an operator conventionally performed visual inspection for review using an electron microscope to discriminate between a scratch showing shape variations and a foreign material, which required a long review time. As a result, measures against a scratch or a particulate foreign material are delayed, which causes a large quantity of wafers to be polished continuously in bad conditions, resulting in a great loss in profit.